A research study is proposed to refine and evaluate a new device to improve the estimation of indoor exposure to inhalable particulate for both children in the first year of life and toddlers. Because they frequently play on the floor, these children may experience significantly higher levels of exposure than older children and adults to PM10 particles and airborne constituents, which are known asthmagens. A total of 200 children ages 6 to 35 months will be enrolled from neighborhood clinics. Parents will be administered a standardized asthma questionnaire (ISAAC) to determine presence and frequency of asthma symtpoms. Exposures will be characterized both qualitatively and quantitatively, to examine if the more precise estimation of PM10 exposure obtained by using a surrogate for personal monitoring. The study will employ a revised iteration of a prototype Pre-Toddler Inhalable Particulate Environmental Robotic (PIPER) Sampler that has been developed and undergone preliminary testing. Sampling will be carried out with both a fixed height stationary sampling station, where inlets of all instruments will be at 110 cm height, and the self- propelled computerized PIPER sampler, where inlets of all instruments can be varied between 20 to 110cm above the floor to mirror the varied breathing heights of these children while engaged in play on the floor. Four parameters will be for each household: 1) mass concentration of PM10 particles measured by a real- time monitoring device;2) real-time particle size and number distribution (0.3-10 urn);3) air sampling on filters for detailed characterization of the PM10 constituents (pesticides, allergens, and endotoxins);4) concentration and composition of airborne fungi (viable and non-viable) collected on glass slides. Measurements will be collected in tandem for each of the 4 types of monitoring. The results of the laboratory analysis for endotoxins, molds and allergens for cockroaches (Bla g Yz), dust mites (Der f 1/p 1), dog (Can f 1), cat (Pel d 1) and mouse (Mus ml) will be evaluated for association with reporting of asthma symptoms This study seeks to provide an alternative to personal monitoring for a variety of environmental exposures that may be experienced by children too young to be assessed by conventional methods, including those in their first year of life. In addition, it will open up an avenue for more precise estimation of early childhood exposures to asthmagens in the PM10 fraction of aerosols.